Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and does real work: it discloses cost ($0.00 to call), the per-route free-call throttle, ordering (core products first), and the fields returned. It stops short of stating rate limits beyond the free-call note or whether the listing is ever cached/stale.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The lead ('Free. List every endpoint ... example query') is well front-loaded, but the following 14-item price enumeration is a dense inline dump that could be collapsed to a range or deferred to the response. It is informative yet heavy for a description field.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema and no annotations, so the description must describe the return shape, and it does: price, description, and example query per endpoint, with core products ordered first. Only a note on response size/pagination is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4; nothing about parameter meaning needs explaining, and the description correctly spends no words on inputs.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a clear verb and resource ('List every endpoint') plus what each entry contains: price in USDC, description, example query. It implicitly separates itself from the per-endpoint siblings (tx_explain, ens, geocode) as the catalog view, but never names a sibling or the discovery role explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Free' and '1 free call per route per caller' hint at when it is cheap to call, but there is no explicit guidance on when to use this versus discovery siblings like apis_search, api_directory_sample, or free_tiers. Usage is implied rather than directed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.